USING CHEAP OLD METERS TO MAKE EITHER A MILLI-VOLTMETER OR MICRO-AMMETER

This article written by Brian Hardcasle, G4DYF, was originally published in SPRAT Autumn 1979 Issue Nr 20

VOLTMETER

FSD R1 R2
1000v 1M 1K
100v 10M 10K
10V 10M 100K
1V 900K 100K
0.1V 0 100K

AMMETER

FSD R1 R2
1A 0 0.1 ohm
100mA 0 1 ohm
10mA 0 10 ohm
1mA 0 100 ohm
500uA 0 500 ohm
100uA 0 1K
10uA 0 10K
1uA 0 100K
This circuit allows a cheap 0-1mA meter to be used as amicro-ammeter or milli-voltmeter.

The +ve and -ve supplies can be of any value between 3 and 18 volts and they need not be symetrical.

The 10k pot is used for zero setting.

If the output from a diode type radiation meter was connected to this circuit, the end product would be a very sensitive field strength meter.

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